1. Field of the Invention
The present invention relates in general to manually operated precision mechanical drives and in particular to an ergonomic dual gear drive system for use in laboratory equipment such as micromanipulators and stereotaxic systems.
2. Description of Prior Developments
Various experimental and investigative procedures are commonly performed on live test specimens such as laboratory animals. These animals, which are often rodents such as rats and mice, are typically secured in a rigidly fixed position during these procedures. It is often desirable to accurately position an instrument such as a pipette, potentiometer, electrode, probe, sensor, laser or other tool adjacent, on or within the specimen, in order to accurately induce and/or monitor various reactions and responses to certain stimuli or other inputs.
The instruments used in these procedures are typically mounted on mechanical slides which are manually driven along a slideway by a lead screw, rack and pinion or other similar drive. In order to operate the slide so as to move the instrument into position, an operator typically rotates a knob which is connected to a gear drive. The gear drive then drives the movable slide over a fixed slideway and thereby moves an attached instrument into and out of position.
In some positioning systems, only a single drive is provided to position an instrument along a slideway. This presents the instrument designer with a choice of using a relatively coarse or high gear ratio drive or a relatively fine or low gear ratio drive. Each type of drive has both advantages and disadvantages.
A high ratio drive allows an operator to quickly move an instrument along the slideway with relatively few turns of a drive knob. This is convenient for quickly moving an instrument from a position remote from a test specimen to a position close to the test specimen and vice versa.
However, such a coarse adjustment is difficult to manipulate so as to achieve small delicate and precision movements of the instrument once it is positioned close to the test specimen. That is, small movements of the rotary drive knob by an operator result in relatively large movements of the instrument, thereby making fine manual adjustments of the instrument difficult to achieve.
If a low ratio drive is provided instead, precision movements and adjustments of the instrument are facilitated, but large movements of the instrument along the slideway are time consuming and inconvenient That is, an operator must complete many turns on the drive knob in order to move the slide and its attached instrument any appreciable distance along the slideway.
It is possible to provide two separate drives for driving an instrument into position. One drive can be a coarse, high speed drive and the other a fine, low speed drive. The first drive can be driven by a first manually operated rotary knob which drives a relatively coarse pitch lead screw drive and the second drive can have a separate, remotely positioned manually operated drive knob which turns a relatively fine pitch lead screw drive.
With two separate drives, an instrument can be brought into close proximity to a test specimen by the high speed, high gear ratio drive, and then an operator can switch over to manipulating a low speed, low gear ratio drive for achieving accurate, final positioning of the instrument.
While a dual drive positioning system of the type noted above can provide both coarse and fine movements of an instrument along a slideway, an operator is somewhat inconvenienced by the required hand movement over some considerable distance from one drive knob to another. That is, the operator""s hand must be moved from one position to another at spaced apart locations on the apparatus to move from one drive knob to another.
This can be distracting to the operator as the operator""s attention must often be intensely focused on the position of the instrument relative to the test specimen. This attention can be broken if the operator has to look away from the instrument to find the other drive knob.
Accordingly, a need exists for an ergonomic dual drive system for quickly and accurately positioning an instrument relative to a test specimen.
A further need exists for such a dual drive system which allows an operator to quickly move an instrument into a desired position with a high speed coarse drive and to subsequently accurately position the instrument into a final position with a low speed fine precision drive.
Yet a further need exists for such a dual drive system which allows an operator to manually switch between coarse and fine instrument drives without the necessity of moving the operator""s hand over any significant distance which would otherwise distract the operator from the precision adjustment of the instrument relative to a specimen.
Still a further need exists for such a dual drive system which includes a pair of drive knobs ergonomically arranged so as to allow an operator to selectively manipulate each drive knob without the need for moving the operator""s focus from the instrument and specimen to the drive knobs.
The present invention has been developed to fulfill the needs noted above, and therefore has as an object the provision of a dual drive system for manipulating positioning apparatus, particularly laboratory apparatus such as precision slides and slideways for moving various instruments and tools into position relative to a workpiece or other specimen such as a laboratory test animal.
A further object of the invention is the provision of a dual drive manipulator which includes a high speed coarse drive and a low speed fine drive, each having a drive knob located ergonomically with respect to the other.
Yet another object of the invention is the provision of such a dual drive manipulator which has a pair of drive knobs coaxially arranged in close proximity so as to allow an operator to maintain a substantially fixed hand position while switching between coarse and fine drives using small, comfortable finger and thumb movements.
Another object of the invention is the provision of a dual drive precision slide for precision instruments which allows an operator to maintain fixed eye focus on the instrument while switching between coarse and fine drives.
Still another object of the invention is the provision of a dual drive manipulator having a high speed or coarse adjustment knob and a low speed or fine adjustment knob each geared to the same single drive screw to avoid tolerance build up associated with multiple drive screw manipulators.
Another object of the invention is the provision of a precision mechanical manipulator having a pair of coaxially mounted drive knobs arranged coaxially with a single drive shaft or lead screw.
A further object of the invention is to provide a manipulator with a dual drive driven by a pair of rotary drive knobs which, when turned in the same direction, (clockwise or counterclockwise) each drives a slide in the same direction (forward or backward). This reduces operator error and potential confusion as to which knob drives the slide in what direction when turned and rotated in a given direction.
These and other objects are met in accordance with the present invention which is directed to a dual gear drive system for moving and positioning tools, sensors or other instruments along a slideway of a precision positioning instrument. The dual gear drive has found particular advantage in laboratory equipment such as micro-manipulators and stereotaxic apparatus.
An important feature of the invention is the coaxial mounting of a low speed or fine rotary drive knob closely adjacent to a high speed or coarse rotary drive knob. The fine rotary drive knob can be mounted closely axially adjacent to the course rotary drive knob to minimize the distance required to move one""s finger and thumb from one knob to the other. This, in turn, allows an operator to maintain eye focus on an instrument and specimen as the operator moves from one drive knob to the other. No gross hand movements are required.
The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof